Abstract

A new class of nonchemically amplified molecular resists has been made based on the use of photosensitive protecting groups. The deprotection during exposure converts a dissolution inhibiting compound into a dissolution promoter. The key benefit of the use of molecular resists in this application is that they can exhibit a sharp solubility transition with relatively low levels of deprotection. Two different inhibiting compounds were made that use a 2-nitrobenzyl protecting group; NBnDCh, an aliphatic molecular resist based on deoxycholic acid, and NBnHPF, based on an aromatic molecular resist containing two phenol groups. Blending these compounds with a calixarene dissolution promoter allowed the contrast and sensitivity of the resist formulations to be tuned. Contrast ratios as high as 27 and deep ultraviolet (DUV) sensitivities between 150 and were obtained using NBnDCh. NBnHPF based systems not only showed somewhat lower contrasts but also exhibited much lower clearing doses of only and smaller. One particular NBnHPF formulation possessed a sensitivity of and a contrast of 8.3, and it was even possible to formulate one resist with an extremely low dose-to-clear value of only . Such low dose-to-clear values in nonchemically amplified resists have, to the authors’ knowledge, not been reported before. The Dill C parameter for each of the two systems was quantified using Fourier transform infrared spectroscopy. The sensitivity of the NBnHPF systems was found to be very good because they undergo a solubility transition at inhibitor; this means that some formulations only need 0.5% photoconversion to pattern. Despite the excellent DUV sensitivity of these systems, it was found that they do not possess high sensitivity when exposed using extreme ultraviolet or e-beam exposure sources.

Received 12 July 2010Accepted 20 September 2010Published online 30 November 2010

Acknowledgments:

The authors gratefully acknowledge Intel Corporation for funding this research and would like to thank Steve Putna, Wang Yueh, and Todd Younkin at Intel for helpful discussions related to this work. The authors would also like to thank Ralph Dammel and AZ Electronic Materials for donating the developers used in this study.